Re: [boost] MPL's "round" lambda

From: David Abrahams (dave_at_[hidden])
Date: 2002-11-18 08:01:45

Aleksey Gurtovoy <agurtovoy_at_[hidden]> writes:

> If you are tired of angle brackets in your templates (no, it's not a TV
> commercial :), may be you'll like this one:
>
>     typedef eval<
>           count_if(
>               list(int,char,long,int)
>             , lambda(is_same(_,int))
>             )
>         >::type res;
>
>     BOOST_STATIC_ASSERT(res::value == 2);
>
> Or this one:
>
>     typedef eval<
>           find_if( 
>               filter_view(
>                   list(int,float,char,long,double)
>                 , lambda(not_(is_float(_)))
>                 )
>             , lambda( or_( 
>                   is_same(_,short)
>                 , less(sizeof_(_),sizeof_(int))
>                 ) )
>             )
>         >::type iter;
>
>     typedef eval< is_same(iter::type,char) >::type res2;
>         
>     BOOST_STATIC_ASSERT(res2::value);
>
> The above actually compiles on Comeau C/C++ 4.3.0.1 and Intel C++ 6.0 with
> the current MPL sources in the CVS; see
> http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/*checkout*/boost/boost/libs/m
> pl/example/lambda2.cpp for an example. Note that the "factorial" snippet
> there doesn't work yet (if you ask 'fact::value', it will blow).

Interesting. Like Dirk, I too am wondering what the point is, beyond
syntactic sugar. I notice the namespace "mpl::v2_1" in the code.
Shouldn't we have completed MPL documentation before moving on to
things like this?

-- 
                       David Abrahams
   dave_at_[hidden] * http://www.boost-consulting.com
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